Process for reducing fish or fish offal



Jan. 2, 1951 c. R. BRADFORD 2,536,345

PROCESS FR REDUCING FISH 0R FISH OFFL Filed May 7, 1948 2 Sheets-Sheet lln v Jan. 2, 1951 c. R. BRADFORD PROCESS FOR REDUCING FISH 0R FISH OFFAL2 Sheets-Sheet 2 Filed May 7, 1948 Patented Jan. 2, 1951 UNITED STATESPATENT OFFICE PROCESS FOR REDUCING FISH E FISH OFFAL Charles RaymondBradford, Los AngeIes,.Calif. Application May 7, 1948, Serial No. 25,716

This invention relates to the reduction of fish or fish ofl'al into ahigh protein content fish meal and a. fish oil and more particularly toa continuous process for so reducing fish or fish oiTal characterized bythe maintenance of a critical ratio of water to oil-free and water-freesolids. Such critical ratio has been discovered to permit continuoussolvent extraction of the oil from the cooked fish or fish offal whileretaining in the meal a very high percentage of the protein content ofthe fish.

In the process of this invention the fish or fish oilal is first cookedin continuously fed screw-type conveyor cookers to a point where thewater content is reduced to the critical range of from 40 to 50 percentby weight, the balance comprising solids and fish oil. It has beendiscovered that this critical concentration permits the solvent sprayedinto the fish in the extractor to extract the oil while meanwhilecoagulating the protein content of the 'fish or fish offal withoutcausing the fish meal to become finely divided and pass into suspension.

4 The invention contemplates the use of a socalled "heavy solvent,preferred examplesbeing heavy chlorinated hydrocarbons, such astrichlorethylene, and perchlorethylene.

In accordance with the discovery of this invention it has been foundthat the critical water concentration in the cooked fish meat undergoingextraction is as above stated and that if insufflcient moisture has beenremoved, the fish or fish oifal will form an agglomerated mass or manysuch masses in the extractor, which masses would adhere tenaciously tothe screw shaft and walls of the extractor. This would result in atendency to plug the extractor with vthe agglomerated masses of fish andhalt the operation. Further, this would prevent adequate washing of themeat with solvent and adequate oil extraction. This, of course, wouldresult in lowered amounts of recovered oil and an undesirably high oilcontent in the final fish meal. Further, if too much moisture has beenremoved in the cookers so that the percentage of water content fallsbelow the critical value, the fish or fish ofal would settle in thesolvent in the extractor and thus be carried out of the extractor in theoverflow pipes for the oil-rich solvent. This would, of course,contaminate the oil, causing problems in the pipe still and strippingstill and result in lowered yields of fish meal.

If, however, the moisture content is maintained at the critical value,the fish or fish oial will neither be agglomerated nor Vsettle in thethe screw conveyor in the extractor it can 12 Clam. (CIL 99-2) solventbut will float therein. In floating to the surface of the solvent and insubsequent upward passage through the extractor, the sh orI fish oiialwill be thoroughly washed by the sprays of fresh solvent,` thusextracting the oil into the solvent and washing all of the oil-richsolvent from the fish or fish oflal. However, the protein content of thefish or fish oal is not dissolved in the solvent, but is coagulated andremains to constitute a substantial part of the solventwashed fish orfish ofial. Further, the fish or fish ofl'al on leaving the extractorwould contain a sorbed solvent having a completely negligible oilcontent. Thus, the maintenance of the critical values results in amaximum recovery of fish oil anda separate recovery of' substantiallyoil-free, high protein-content sh meal, and a continuous operation ofthe process is: not hampered by an excessive amount of sh or fish oialcarried over with the oil from the extractor. Likewise,` when themoisture content is maintained at the critical value the particles ofsolids tend to cling to each other in small masses in the presence ofthe solvent so that the consistency of the mass is such as to makepositive conveyance upwards; through a` screw conveyor possible, and asthe fish or iish ofi'al passes upwards through be thoroughly washed bythe solvent.

The process; further contemplates the drying of the fish meal after itleaves the extractor for the recovery o1' the sorbed solvent. The watercontent of the fish meal still remaining substan tially unchanged inpassage through the extractor provides what in eiect amounts to a steamstripping of the fish meal in the dryers, thus facilitating recovery ofthe solvent, and, if desred, additional steam may be applied in a steamstripper. The solvent may be recovered in condensers and recirculated.The oil-rich solvent upon leaving the extractor is subjected todistillation and steam stripping to separate the solvent and to purifythe oil. The solvent recovered in this series of operations is alsorecirculated to the extractor.

The process of this invention also contemplates that all vapors andgases are completely confined and all uncondensed vapors or gases may bescrubbed prior to venting to the atmosphere to remove objectionableodorsl thus eliminating the usual odors surrounding a fish reductionplant.

It is therefore one object of this invention to provide a continuousfish reduction process and apparatus resulting in a high recovery ofilsh oil and a separate high recovery of substantially oil-free, highprotein-content fish meal.

It is a further object of this invention to provide such a continuousreduction of iish in which a critical concentration of water in the iishundergoing solvent extraction is maintained.

It is a further object of this invention to maintain in a continuousiish reduction plant a critical concentration of water in the fishundergoing solvent extraction which concentration is reducedsufficiently to prevent the formation of agglomerated masses of iishlikely to plug the apparatus and likely to prevent adequate washing ofthe iish with the solvent.

It is a further object of this invention to maintain in a continuousfish reduction plant a critical concentration of water in the iishundergoing extraction which concentration is suicient to preventsettling of the fish meat in the solvent which would result in the iishpassing out of the extractor in the pipes provided for the oil-richsolvent.

It is a further object of this invention to maintain in a. continuousiish reduction plant a critical concentration of water in the fish oriish oial undergoing extraction such that the particles of iish meatcling to each other in the presence of the solvent with a consistencysuch as to make possible a positive conveyance of the ish meat upwardsthrough they screw conveyor countercurrent to a continuous wash of freshsolvent.

It is a further object of this invention to use in a continuous ilshreduction plant a heavy solvent, such as trichlorethylene which solventis capable or extracting the oil from the fish or sh oial andcoagulating the protein content of the sh v undergoing extraction so asto make possible the production of a low oil-content, highproteincontent iish meal.

`It is a further object of this invention to provide a novel iishreduction apparatus or plant for continuously cooking and extracting thesh, drying the iish meal, and distilling the solvent from iish oil inaccordance with the abovedescribed process.

These and further objects and advantages of the present invention willbe apparent in the annexed specification, in which:

Figure 1 is a diagrammatical view of the apparatus of this invention.

Figure 2 is an enlarged section through the extractor of this invention.

Figure 3 is a cross section through the surge tank shown in Figure l.,

Figure 4 is an enlarged cross section taken along the line 4--4 ofFigure 2.

Figure 5 is an enlarged perspective elevation oi. a section of the screwconveyor used in the cookers and dryers.

Figure 6 is a similar enlarged perspective elevation of a section of thescrew conveyor used in the extractor. i

Referring now more particularly .tothe drawings, there is shown a hopperI Il feeding a feed screw I2 leading to a cooker I4. 'I'he cooker I4 isprovided with a feed screw (not shown) for advancing the ilsh undertreatment along' the cooker and has a steam jacket I5 partiallysurrounding the cooker as indicated. The return bend I5 `leads to asimilar cooker 22 similarly provided with a` feed screw, in this casefeeding the iish` in the opposite direction.` A similar steam jacket 23is provided on the cooker 22. A vapor pipe I1 leading to a condenser I8is provided in communication with the cookers I4 and 22 by means ofwhich vapors and water from the fish are condensed and passed by meansof the line I9 to a separator 20.

Fish from the cooker 22 is passed through a pipe 24 to feed screw 25.The feed screw 25 as shown in Figure 2 comprises a tubular member 25ain'which is disposed a` screw conveyor 25h and a header 26 is providedhaving a plurality of spray pipes 21 thereon for spraying solvent on thefish meat being passed along the feed screw 25. A vapor line 28'communicates with the feed screw 25 and leads to the condenser 30 andthence to the separator 20. From the feed screw 25 the cooked fish andsolvent is passed by pipe 3l to the extractor 32. The extractor 32comprises a tubular member 32a, preferably pitched at an angle of from 0to 30 from horizontal, and a screw conveyor 32h is mounted therein withthe bottom flights of the screw conveyor in iirm, sliding contact withthe bottom of the tube 32a and with a free space, in practiceapproximating one inch, between the top flights of the screw and theinternal dimension of the top of the tube 32a as clearly indicated inFigure 2. l

In the extractor 32 the fish is fed continuously upward by means of theconveyor 32h and sub- -jected to a countercurrent of solvent sprayedover the iish by means of a header 34 and spray ppes 35. In the drawingssix of the spray pipes 35 have been illustrated, but it will beappreciated that any number of pipes may be used to vary the rate ofsupply of solvent within the purview of this invention.

From the extractor 32 sh solids are passed by a pipe 38 to a series ofdryers 39, 40, and 4I, respectively. Each of the dryers has a steamjacket 42, and vapor from the dryers 39, 40, and 4I is passed by vaporlines 43 to a condenser 44 thence to the line to the separator 20. Fromthe iinal dryer 4I extracted and dried iish meal suitable for grindingis fed through a pipe 48 to discharge pipe 49.

Solvent is continuously passed from the extractor 32 by a. solvent line50 to a surge tank 52. The solvent line 50 is provided with a stand pipe5I, forming a header from which a plurality of valves 5 Ia are suspendedand spaced in vertical relation. As will be apparent, by suitableselection of the valve 5Ia to open to pass oil the solvent from theextractor, the level of solvent in the extractor 32 may be regulated atwill. Rich solvent from the surge tank 52 is fed by line 54 and pump 55to a still 56 from whence the vapors are passed to a separator 58. Fromthe separator 58 vapors are passed by aline 59 to a condenser 60 andthence through the pump 62 to the separtor 20. Also, from the separator58 the recovered ilsh oil is passedfby the line 64 and pump 65 to thesteam stripper 66. Vapors from the steam stripper 65 are passed by theline 88 to the condenser 30 and thence by the line 69 to the separator20. Fish oil from the steam stripper 56 is passed by the line 10 andpump 'Il to storage.

In the separator 20 condensate from the condenser I8, the condenser 44,the condenser 30, and the condenser 50 in the aggregate, including allgases, water, .and solvent extracted, are separated, water beingcontinuously taken through the line and passed to the sewer,

at' the top through pipe 32. The water having absorbed the odorous gasesis passed to `the sewer through pipe 83, the gases vented from thescrubber 86 being completely clean and odorless. A solvent feed line 90is provided continuously passing solvent from the solvent storage tank83 by means of the pump 8l to the solvent spray headers 34 and 26.

Each of the members I2, il, 22, 38, 40, and 4I comprises essentially apipe in which is located a leftor right-hand continuous screw.

The cookers i4 and 22 and the dryers 39-4I employ the type of ribbonscrew shown in Figure 5 in which a tumbling bar |00 is connected betweenadjacent flights of the screw for scraping the fish from the bottom ofthe cookers and dryers and stirring and agitating the fish to preventburning thereof while the screw conveyor of the extractor 32 is acontinuous solid screw, as shown in Figure 6, disposed eccentrically ofthe extractor 32 as indicated in Figure 4.

As stated before, the extractor 32 is inclined from the horizontal, andin practice I have found that angles of inclination from to 32,depending upon the type of fish, seem to be the limits of inclination,and preferably for most fish, particularly for tuna, an inclination ofapproximately 20 from the horizontal is desirable.

In carrying out the process fish placed in the hopper I0 is fed by thescrew conveyor I2 to the cookers Il and 22 wherein it is dried to thecritical water content of from 40 per cent to 50 per cent. The fish isthen fed by the screw conveyor 25 to the extractor 32 being given a,preliminary solvent wash in the screw conveyor 25 and being subjected toa countercurrent solvent wash in the solvent extractor 32 as well as abath of solvent, the level of which is maintained by a selection of asuitable valve ta on the line 50. Oilrich solvent is then fed to thesurge tank 52 to the still 56 andseparator 58. Oil from the separator 58is purified in the steam stripper 65 and represents one of the finalproducts. Meanwhile, solids from the extractor 32 are fed to the dryers39, 40, and 4| wherein they are dried, and any entrained solvents andvapors are dissipated. 'I'he solids emerging from the pipe 49 are driedfish meal forming one of the products of this invention.

As noted hereinbefore, vapors are taken off wherever generated,condensed in the condensers and passed to tne separator 20 wherein thesolvent is recovered and fed to the solvent storage tank 83 forrecirculation, uncondensed gases and vapors' being scrubbed in thescrubber 86 prior to venting to the atmosphere to remove objectionableodors.

It will thus be apparent that by means of this invention a. continuousoperation of a solvent oil vextraction plant has been achieved, and inthe process of so continuously extracting the fish oil, I have been ableto obtain an increased protein content in the fish meal, an example ofthe increase obtained -being apparent from typical tests in whichidentical tuna oifal was treated by conventional pressing methods, thefinal protein content of the pressed meal equaling 60.69 per cent, withthe final protein content of the meal processed by this inventionequaling 73.44 per cent.

has been described what is at present considered a preferred form of theapparatus, it will be appreciated by those skilled in the art thatvarious changes and modifications be made therein without departing fromthe essence of the invention, and it is intended to cover therein al1such changes and modifications as come within the true spirit and scopeof the appended claims.

What is claimed is:

1. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish t0 reduce thewater content thereof to a critical range of from i0 per cent to 50 percent by weight; continuously passing ,the cooked fish to acountercurrent wash of organic solvent to dissolve the fish oil from thefish and coagulate the protein in the fish meal; and separatelyrecovering the fish oil from the solvent and drying the separated fishmeal.

2. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of chlorinated hydrocarbon solvent to dissolve the fish oil fromthe fish and coagulate the protein in the fish meal; and separatelyrecovering the sh oil from the solvent and drying the separated fishmeal.

3. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of' from 40 per cent to'50 percent by weight; continuously passing the cooked fish to countercurrentwash of chlorinated hydrocarbon solvent selected from the, groupcomprising trichlorethylene or perchloroethylene to dissolve the fishoil from the fsh and coagulate the protein inthe fish meal; andseparately recovering the fish oil from the solvent and drying theseparated .sh meal.

4. The method of continuously reducing :sh to fish mealand -`fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 perkcentby weight; conf tinuously passing the cooked fish to acountercurrent wash of trichlorethylene solvent to dis-A solve the fishoil from the fish and coagulate the protein in the fish meal; andseparately recovering the fish oil from the solvent and drying theseparated fish meal.

5. The method of continuously reducing fish K to sh meal and fish oilwhich comprises 'the While there has been described a particularapparatus for carrying out the process of the present. invention, itwill be appreciated that this is merely a preferred form of apparatusfor facilitating the carrying out of the process of the invention andthe process is by no means limited Vte. the particular apparatusillustrated; and while there steps of' continuously cooking the fish toreduce the water content thereof to a critical range of from 40 per centto 50 per cent by weight; continuously passing the cooked fish to acountercurrent wash of perchlorethylene solvent to dissolve the fish oilfrom the fish and coagulate the protein in the fish meal; and separatelyrecovering the fish oil from the solvent and .drying the separated fishmeal.

6. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce.the water content thereof to al critical range of from 40 per cent to50 per cent by weight; continuously passing the cooked fish to acountercurrent wash of organic solvent sufficient to saturate saidcooked fish with said solvent to dissolve the fish oil from the fish andcoagulate the protein in the fish meal; and separately recovering thefish oil from the solvent and drying the separated sh meal.

7. The method of continuously reducing fish to fish .meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of organic solvent to dissolve the fish oil from the fish andcoagulate the protein in the ffish meal; washing the fish withadditional solvent to separate out the oil-rich solvent; and separatelyrecovering the fish oil from the solvent and drying the separated fishmeal.

8. The method of continuously reducing fish to fish meal and fish oilwhich comprisesv the steps of continuously cooking the fish to reducethe water content thereof to a critical range of from 40 per cent to 50per cent by weight; continuously passing vthe cooked fish to acountercurrent wash of chlorinated hydrocarbon solvent to dissolve thefish oil from the fish and coagulate the protein in the fish meal;washing the fish with additional solvent to separate out the oil-richsolvent; and separately recovering the fish cil from the solvent anddrying the separated fish meal.

9. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of trichlorethylene solvent to dissolve the fish oil from the fishand coagulate the protein in the fish meal; washing the fish withadditional solvent to separate out the oil-rich solvent; and separatelyY recovering the fish oil from the solvent and drying the separated shmeal.

10. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of perchlorethylene solvent to dissolve the fish oil from the.-fish and coagulate the protein in the fish meal; washing the fish withadditional solvent to separate out theoil-rich solvent; and separatelyrecovering the fish oil from the solvent and drying the separated fishmeal.

11. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of organic solvent to dissolve the fish oil from the fish andcoagulate the protein in the sh meal; washing the fish with additionalsolvent to separate out the oil-rich solvent; separately recovering thefish oll from the solvent and drying the separated fish meal; andcontinuously collecting all solvent bearing vapors from the cooking anddrying steps as well as the solvent from the oil separation steps andrecovering the solvent for recirculation.

12. The method of continuously reducing fish to fish meal and fish oilwhich comprises the steps of continuously cooking the fish to reduce thewater content thereof to a critical range of from 40 per cent to 50 percent by weight; continuously passing the cooked fish to a countercurrentwash of organic solvent to dissolve the fish oil from the fish andcoagulate the proteinln the fish meal; washing the fish with additionalsolvent to separate out the oil-rich solvent; separately recovering thefish oil from the solvent and drying the separated fish meal;continuously collecting all solvent bearing vapors from the' cooking anddrying steps as well as the solvent from the oil separation steps andrecovering the solvent for recirculation; and scrubbing all uncondensedgases from said solvent recovery steps to deodorize said gases.

CHARLES RAYMOND BRADFORD.

REFERENCES CITED The following references are of record in the file ofthis patent:

Mortenson Feb. 18, 1947

1. THE METHOD OF CONTINUOUSLY REDUCING FISH TO FISH MEAL AND FISH OILWHICH COMPRISES THE STEPS OF CONTINUOUSLY COOKING THE FISH TO REDUCE THEWATER CONTENT THEREOF TO A CRITICAL RANGE OF FROM 40 PER CENT TO 50 PERCENT BY WEIGHT; CONTINOUSLY PASSING THE COOKED FISH TO A COUNTERCURRENTWASH OF ORGANIC SOLVENT TO DISSOLVE THE FISH OIL FROM THE FISH ANDCOAGULATE THE PROTEIN IN THE FISH MEAL; AND SEPARATELY RECOVERING THE